Figure 1.

Structures of wild-type, neoΔHS, and ΔneoΔHS GATA-1 alleles. The wild-type locus contains alternative first exons (IT and IE) and a DNase I HS region (10). Exons are indicated by solid boxes. In the neoΔHS locus a loxP-flanked neomycin-resistance cassette replaces ≈8 kb lying between a BamHI site (B) and an artificial XhoI site (〈Xh〉) present in a λ phage genomic clone used in the construction. Cre-mediated excision of the neomycin-resistance cassette leaves a single loxP site (indicated by the solid triangle) in the ΔneoΔHS locus.